704 research outputs found
Singlet-triplet transition in a few-electron lateral InGaAs-InAlAs quantum dot
The magnetic-field evolution of Coulomb blockade peaks in lateral
InGaAs/InAlAs quantum dots in the few-electron regime is reported. Quantum dots
are defined by gates evaporated onto a 60 nm-thick hydrogen silsesquioxane
insulating film. A gyromagnetic factor of 4.4 is measured via zero-bias spin
spectroscopy and a transition from singlet to triplet spin configuration is
found at an in-plane magnetic field B = 0.7 T. This observation opens the way
to the manipulation of singlet and triplet states at moderate fields and its
relevance for quantum information applications will be discussed.Comment: 4 pages, 3 figure
Electrostatic tailoring of magnetic interference in quantum point contact ballistic Josephson junctions
The magneto-electrostatic tailoring of the supercurrent in quantum point
contact ballistic Josephson junctions is demonstrated. An etched InAs-based
heterostructure is laterally contacted to superconducting niobium leads and the
existence of two etched side gates permits, in combination with the application
of a perpendicular magnetic field, to modify continuously the magnetic
interference pattern by depleting the weak link. For wider junctions the
supercurrent presents a Fraunhofer-like interference pattern with periodicity
h/2e whereas by shrinking electrostatically the weak link, the periodicity
evolves continuously to a monotonic decay. These devices represent novel
tunable structures that might lead to the study of the elusive Majorana
fermions.Comment: 4.5 pages, 4 color figure
Switching the sign of Josephson current through Aharonov-Bohm interferometry
We investigate the DC Josephson effect in a superconductor-normal
metal-superconductor junction where the normal region consists of a ballistic
ring. We show that a fully controllable -junction can be realized through
the electro-magnetostatic Aharonov-Bohm effect in the ring. The sign and the
magnitude of the supercurrent can be tuned by varying the magnetic flux and the
gate voltage applied to one arm, around suitable values. The implementation in
a realistic set-up is discussed.Comment: 4 pages, 3 figure
High critical-current density and scaling of phase-slip processes in YBaCuO nanowires
YBaCuO nanowires were reproducibly fabricated down to widths of 50 nm. A
Au/Ti cap layer on YBCO yielded high electrical performance up to temperatures
above 80 K in single nanowires. Critical current density of tens of MA/cm2 at T
= 4.2 K and of 10 MA/cm2 at 77 K were achieved that survive in high magnetic
fields. Phase-slip processes were tuned by choosing the size of the
nanochannels and the intensity of the applied external magnetic field. Data
indicate that YBCO nanowires are rather attractive system for the fabrication
of efficient sensors, supporting the notion of futuristic THz devices.Comment: 8 pages, 3 figures. Accepted for publication in Superconductor
Science and Technolog
Enhancing sustainability by improving plant salt tolerance through macro-and micro-algal biostimulants
Algal biomass, extracts, or derivatives have long been considered a valuable material to bring benefits to humans and cultivated plants. In the last decades, it became evident that algal formulations can induce multiple effects on crops (including an increase in biomass, yield, and quality), and that algal extracts contain a series of bioactive compounds and signaling molecules, in addition to mineral and organic nutrients. The need to reduce the non-renewable chemical input in agriculture has recently prompted an increase in the use of algal extracts as a plant biostimulant, also because of their ability to promote plant growth in suboptimal conditions such as saline environments is beneficial. In this article, we discuss some research areas that are critical for the implementation in agriculture of macro-and microalgae extracts as plant biostimulants. Specifically, we provide an overview of current knowledge and achievements about extraction methods, compositions, and action mechanisms of algal extracts, focusing on salt-stress tolerance. We also outline current limitations and possible research avenues. We conclude that the comparison and the integration of knowledge on the molecular and physiological response of plants to salt and to algal extracts should also guide the extraction procedures and application methods. The effects of algal biostimulants have been mainly investigated from an applied perspective, and the exploitation of different scientific disciplines is still much needed for the development of new sustainable strategies to increase crop tolerance to salt stress
Enhancing Sustainability by Improving Plant Salt Tolerance through Macro- and Micro-Algal Biostimulants
Algal biomass, extracts, or derivatives have long been considered a valuable material to bring benefits to humans and cultivated plants. In the last decades, it became evident that algal formulations can induce multiple effects on crops (including an increase in biomass, yield, and quality), and that algal extracts contain a series of bioactive compounds and signaling molecules, in addition to mineral and organic nutrients. The need to reduce the non-renewable chemical input in agriculture has recently prompted an increase in the use of algal extracts as a plant biostimulant, also because of their ability to promote plant growth in suboptimal conditions such as saline environments is beneficial. In this article, we discuss some research areas that are critical for the implementation in agriculture of macro- and microalgae extracts as plant biostimulants. Specifically, we provide an overview of current knowledge and achievements about extraction methods, compositions, and action mechanisms of algal extracts, focusing on salt-stress tolerance. We also outline current limitations and possible research avenues. We conclude that the comparison and the integration of knowledge on the molecular and physiological response of plants to salt and to algal extracts should also guide the extraction procedures and application methods. The effects of algal biostimulants have been mainly investigated from an applied perspective, and the exploitation of different scientific disciplines is still much needed for the development of new sustainable strategies to increase crop tolerance to salt stress
Durum wheat roots adapt to salinity remodeling the cellular content of nitrogen metabolites and sucrose
Plants are currently experiencing increasing salinity problems due to irrigation with brackish water. Moreover, in fields, roots can grow in soils which show spatial variation in water content and salt concentration, also because of the type of irrigation. Salinity impairs crop growth and productivity by inhibiting many physiological and metabolic processes, in particular nitrate uptake, translocation, and assimilation. Salinity determines an increase of sap osmolality from about 305 mOsmol kg-1 in control roots to about 530 mOsmol kg-1 in roots under salinity. Root cells adapt to salinity by sequestering sodium in the vacuole, as a cheap osmoticum, and showing a rearrangement of few nitrogencontaining metabolites and sucrose in the cytosol, both for osmotic adjustment and oxidative stress protection, thus providing plant viability even at low nitrate levels. Mainly glycine betaine and sucrose at low nitrate concentration, and glycine betaine, asparagine and proline at high nitrate levels can be assumed responsible for the osmotic adjustment of the cytosol, the assimilation of the excess of ammonium and the scavenging of ROS under salinity. High nitrate plants with half of the root system under salinity accumulate proline and glutamine in both control and salt stressed split roots, revealing that osmotic adjustment is not a regional effect in plants. The expression level and enzymatic activities of asparagine synthetase and δ1-pyrroline-5-carboxylate synthetase, as well as other enzymatic activities of nitrogen and carbon metabolism, are analyzed
Modelling the Canes Venatici I dwarf spheroidal galaxy
The aim of this work is to find a progenitor for Canes Venatici I (CVn I),
under the assumption that it is a dark matter free object that is undergoing
tidal disruption. With a simple point mass integrator, we searched for an orbit
for this galaxy using its current position, position angle, and radial velocity
in the sky as constraints. The orbit that gives the best results has the pair
of proper motions = -0.099 mas yr and = -0.147
mas yr, that is an apogalactic distance of 242.79 kpc and a perigalactic
distance of 20.01 kpc. Using a dark matter free progenitor that undergoes tidal
disruption, the best-fitting model matches the final mass, surface brightness,
effective radius, and velocity dispersion of CVn I simultaneously. This model
has an initial Plummer mass of 2.47 x M and a Plummer radius of
653 pc, producing a remnant after 10 Gyr with a final mass of 2.45 x 10
M, a central surface brightness of 26.9 mag arcsec, an effective
radius of 545.7 pc, and a velocity dispersion with the value 7.58 km s.
Furthermore, it is matching the position angle and ellipticity of the projected
object in the sky.Comment: 11 pages, 14 figures, accepted by A&
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